This invention relates to an electromagnetic plunger having a built-in electromagnetic valve means.
Generally, a pump may be used to draw a liquid by suction from a position which is disposed at a higher level than the pump itself and to discharge the same after delivering it under pressure to the desired destination, or may be used to draw a liquid by suction from a position which is disposed at a lower level than the pump itself and to eject the same after delivering it under pressure to the desired destination. In such case, the pressure of the head of the liquid may open the suction valve or the discharge valve of the pump to cause the liquid to ooze or leak out while the pump is inoperative, or the liquid may be caused to eject through the valve by the pressure of the head till the pressure on the discharge side of the pump falls. In order to avoid such trouble, it has hitherto been customary to provide the pump with an electromagnetic valve which is mounted at the discharge side of the pump as an independent unitary member so as to thereby interrupt the discharge of the liquid when the pump is rendered inoperative.
Electromagnetic plunger pumps each having a built-in electromagnetic valve include an electromagnetic piston pump of the solenoid type disclosed in Japanese Laid-Open Patent Gazette No. Sho 48-82407 (Japanese patent application Ser. No. Sho 47-12037) and a plunger pump of the solenoid type which may also employ an electromagnetic valve disclosed in Japanese Laid-Open Pat. Gazette No. Sho 49-21703 (Japanese patent application Ser. No. Sho 47-61308). In either case, the liquid flows through the electromagnetic plunger case to the discharge port of the pump, with the electromagnetic means being a part of the magnetic head or a composite magnetic head. Thus it has been difficult or almost impossible to provide the electromagnetic means on the magnetic head, on the vertical axis of the electromagnetic coil or on the extension of the electromagnetic coil where the discharge capacity of the pump can be readily adjusted. The electromagnetic means of the prior art has also been inconvenient to operate.